1. Field of the Invention
The present invention relates generally to an actively controlled suspension system for controlling suspension characteristics depending upon the vehicle driving condition. More specifically, the invention relates to a power supply control system for an actively controlled suspension system in which suspension control is maintained active after turning OFF of a main power switch, i.e. an ignition switch.
2. Description of the Background Art
Actively controlled suspension systems have gained popularity in automotive vehicles because of remarkable performance in achieving both driving stability and riding comfort. Such suspension systems perform various controls, such as anti-rolling and/or anti-pitching control, bounding suppressive control and so forth, for regulating vehicular body attitude at various vehicle driving mode conditions.
In general, bouncing suppressive suspension control is performed for suppressing relative displacement between a vehicle body and a suspension member which rotatable supports a road wheel. Relative displacement between the vehicle body and a suspension member is monitored by means of sensors, such as a vertical acceleration sensor, a stroke sensor and so forth.
In practice, suspension control is performed by regulating a vehicular height at a predetermined height level for suppressing vehicular attitude change. Therefore, vehicular height level is maintained at the predetermined height level as long as the suspension control is active. However, when an ignition switch is turned OFF, the fluid pressure in the working chamber is rapidly drained to the pressure source unit, in which fluid pressure is droped to zero in response to termination of engine driving. As a result, unintended vehicular height variation occurs in response to turning OFF of the ignition switch. This clearly reduces riding comfort.